A replica system can be used to recover data when data in a primary system is corrupted or lost. Multiple primary systems can be serviced by a single replica system. For efficiency of storage, both the replica system and the primary systems may be deduplicating systems. In a deduplicating system, incoming data is broken up into segments, and if the segment is already stored on the system, a reference to the already-stored segment is stored instead of storing the segment again.
However, although deduplication can result in a substantial reduction in the amount of space required to store data for a single system, deduplication requires garbage collection to determine which segments are duplicated when deleting data. In addition, more processing may be required for garbage collection in a replica system because for a replica system that replicates data from multiple primary systems there may be additional deduplication possible since an identical segment may be stored on more than one primary system.